By way of brief background, conventional wireless power transmission can allow a receiving device to receive power that is transmitted wirelessly, though typically line-of-sight, to the receiving device. Wireless power transmission can cause a higher energy density in a region. A receiving device in that higher energy density region can generate power from the higher energy density, e.g., a phone can charge wirelessly when placed in a region of higher energy density caused by transmission of radio frequency (RF) energy to the region.